This disclosure relates to medical devices and more particularly to an implantable lead.
The medical device industry produces a wide variety of electronic and mechanical devices for treating patient medical conditions such as pacemakers, defibrillators, neuro-stimulators and therapeutic substance delivery pumps. Medical devices can be configured to be surgically implanted or connected externally to the patient receiving treatment. Clinicians use medical devices alone or in combination with therapeutic substance therapies and surgery to treat patient medical conditions. For some medical conditions, medical devices provide the best and sometimes the only therapy to restore an individual to a more healthful condition and a fuller life. One type of medical device is an implantable neurological stimulation system that can be used to treat conditions such as pain, movement disorders, pelvic floor disorders, gastroparesis, and a wide variety of other medical conditions. The neurostimulation system typically includes a neurostimulator, a stimulation lead, and an extension such as shown in Medtronic, Inc. brochure “Implantable Neurostimulation System” (1998). More specifically, the neurostimulator system can be an Itrel II® Model 7424 or an Itrel 3® Model 7425 available from Medtronic, Inc. in Minneapolis, Minn. that can be used to treat conditions such as pain, movement disorders and pelvic floor disorders. The neurostimulator is typically connected to a stimulation lead that has one or more electrodes to deliver electrical stimulation to a specific location in the patient's body.
Implantable leads have conductors that are connected to contacts to form electrical paths. The connection between the conductors and the contacts should have a solid mechanical connection and a low impedance electrical connection for efficient operation and reliability. Conductors manufactured from low impedance materials such as silver make forming a connection with good mechanical properties challenging because silver has substantially less tensile strength than a more common conductor material such as MP35N. Additionally, silver content in the weld joint between a conductor and contact increases the chances of separation, silver exposure to tissue, and weld corrosion during lead operation. Some previous connections directly connect the conductor to the contact but sometimes the conductor material is not ideal for forming a strong mechanical connection. Additionally, conductor material such as conductor ions can migrate from the conductor to the contact or even from the conductor into the patient. Other previous connections use a tube crimped to the conductor that is welded to the contact. Although the tube can improve the mechanical connection, material from the conductor can still migrate from the conductor to the contact or into the patient. An example of a lead with a joined conductor and electrode is shown in U.S. Pat. No. 6,181,971 “Joining Conductor Cables And Electrodes On A Multi-Lumen Lead Body” by Doan (Jan. 30, 2001).
For the foregoing reasons, there is a need for an implantable lead with isolated contact couplings to reduce the opportunity for conductor material to migrate to the contact or into the patient.